But, they're not "writing" for the N1X. That CPU is going to be running windows (purportedly), so any windows games should be able to run on this new CPU. ITs true that some development work to make them native will be required, but its not any different when Qualcomm came out with CPU for windows, I don't think there was much talk about Mac's market share increasing because of that either.
I don't see this as a positive or a negative in terms of mac gaming.
btw, here's some info on the N1X, from Jayztwocents.